1. Field of the Invention
Embodiments of the present invention relate generally to image display devices and, more specifically, to systems and methods for adjusting optical power output for multiple light sources in a display device to produce a more uniform image.
2. Description of the Related Art
Electronic display systems are commonly used to display information from computers and other sources. Typical display systems range in size from small displays used in mobile devices to very large displays, such as tiled displays, that are used to display images to thousands of viewers at one time. Multiple light sources are commonly used in such displays. For example, in laser-phosphor displays (LPDs), multiple lasers may be used to simultaneously “paint” different phosphor-containing regions to produce an image for a viewer, where the optical output energy of each laser paints a different phosphor-containing region of the display.
Because the human eye can readily perceive small differences in brightness uniformity of a displayed image, the use of multiple light sources in a display system can produce visual artifacts in an image when the output of each light source is not tightly controlled. Differences in brightness as small as 1% within 1 degree angle subtended at the eye between adjacent light sources are apparent to a viewer, so each light source of a display system must be calibrated to generate light energy with a variation of less than 1% from the other light sources. Otherwise, display system brightness will appear non-uniform. For example, in LPDs, in which each laser may illuminate a different row of pixels on a display screen, lines of higher or lower brightness may be apparent to the viewer if the mismatch in laser power is greater than approximately 1% within 1 degree angle subtended at the eye.
Due to manufacturing variations between each laser and drift in the performance of each laser over time, such display devices can frequently have one or more under-performing lasers, which produce regions on the display screen that are noticeably darker to the viewer. To preserve uniformity of image brightness, all other lasers in the display device can be reduced in power to match the optical power output of the under-performing laser. However, this approach can severely reduce image brightness, which is an important component of perceived image quality.
As the foregoing illustrates, there is a need in the art for an improved way to provide uniform optical power adjustment between multiple laser light sources in a display device without unduly dimming and reducing the perceived quality of the image being displayed.